Method and means for making sound amplifiers



Aug- 18 1931- J. B. HAWLEY 1,819,328

METHOD AND MEANS'FOR MAKING SOUND AMPLIFIERS Original Filed Sept. 26. 1924 2 Sheets-Sheet 1 Aug. 18, 1931. J. B. HAwl-.EY 1,819,328

' METHOD AND MEANS FOR MAKING SOUND AMPLIFIERS Original Filed Sept. 26. 1924 2 Sheets-Sheet 2 Patented Aug. is, 1931 1,819,328

.UNITED STATES PATENT OFFICE-- JESSE BARNUM HAWLEY, F ST. CHARLES, ILLINOIS METHOD AND MEANS FOR MAKING SOUND .AMPLIFIERS y Original application led September 26, 1924, Serial No. 740,009. Divided and this application led May 27,

1927. Serial No. 194,686..

This invention relates to the method of rosin, asphalt, drying oils or the like, wheremaking sound amplifying horns, particularly by they are compacted to not only render the adapted for use with phonographs and radio horn more durable but also to provide an exapparatus. terior coating of fiber relatively harder than This is a divisionI of my copending applithecentral fiber portion of the horn wall; and ll cation Serial N o. 7 40,009, filed September 26, in addition to render the horn wall surfaces` 1924, issued as Patent 1,641,630 dated Septemrelatively smooth and hard so as to reflect the ber 6, 1927 sound waves emitted from the horn; to pro- Among the objects of my invention are to vide for removing the blank from a former l0 provide a novel'method fora sound amplifywherein such means is provided with holding 60 ing horn which will produce the maximum, members or devices such as hooks engaging uniform amplification of the sound througliwith the former for holding the same upon the r out the practical range of vibration of the support when the pneumatic pressure is apsound vibrations, with minimum resonance plied to release the blank from the former; to

5 and efficient reflection of the sound waves; to provide for an improved surface for the pre- 65 provide acnovel process for manufacturing formed blank b impregnating the surface the horns on a commercial scale in a simple, with suitable su stances to provide a hard, cheap and practical manner and in a manner finished and compacted surface; to provide which readily lends itself to the production for a hard and brilliant surface as above indi- 0 of any desired type or design of horn;to procated, and further finishing if desired, by 70 r vide for an improved sound amplifying horn stippling the surface material, and then coatcomposed relatively of soft material such as ing with varnish, paint or other substance accretions of interlaced fiber, preferably, but upon the surface of the blank; and, to provide not essentially, of pulp fiberfwherein the for such other and further objects, capabil- 5 superficial fibers forming the horn Walls are ities and advantagesas will later appear and impregnated with a hardening agent to are inherently possessed by the invention. render the horn walls substantially non-re- In the drawings, illustrating the invention, sonant and more durable; to provide an im- Fig. l is a view partly in vertical elevation proved process for making sound amplifying and partly in vertical section of the apparal orns such that the density and, or, thickness tus for forming the blanks upon a plurality of the horn wall can be varied at will and parof ,formera ticularly a process'for forming a horn wall F ig. 2 is a detailed and fragmentary top of variant densities; to provide for a sound plan view of a part of the same. amplifying horn composed of accretions of Fig. 3 is a longitudinal sectional view taken interlaced fiber, the superficial fibers being through the former with the portions thereof l harder so that the fiber horn wall comprises detachably secured together. an inner zone of relatively soft fibers and Fig. 4 is a perspective view of the apparaouter zone of relatively harder fibers, which tus for `loosening or releasing the blanks from construction is most efiicient in dampening the former. resonance,- to further provide fora horn thus Fig. 5 is a longitudinal sectional view of a 9,0 constructed and wherein the harder surface bl nk. fibers are suitably finished to provide smooth And, Fig. 6 is a view in elevation of the sound reflecting surfaces for augmenting the two portions ofthe former ready to be atamplification and for rendering the fib er Walls tached together. more durable; to provide a novel method, The .novel method for making the horn will of forming a horn as hereinbefore-set forth u perhaps be best explained by a description where the horn as thus formed of accretions of of the apparatus for making'the horn. interlaced fibers is surface hardened by im- Referring more particularly to the drawpregnating the superficial fibers with any deings, an apparatus for forming the blank is sired hardening agent such as liquid glue, shown in Fig. 1, and comprises a container 100 or tank 1 in which may be contained a fluidal mass of fibrous material 2 held in suspension in a suitable liquid, such as water, and in more or less homogeneous condition. Suitable stirring or agitating means is used to maintain a thorough suspension of the fibrous material in the solution. At the upper ends of the walls of the tank inlet conduits 3 are provided through which the fibrous material is fed to the containerl. Upon the end walls of the container are also provided channels -4 which act as guides for a support 5 having end tongues 6 capable of sliding vertically in the tracks4." The support 5 extends they length of the container and is provided with a plurality of' ports 6a over which maybe located a plurality of porous horn-shaped formers 7 arranged as clearly shown in Fig. 1 of the drawings. The ports 6 are connected may be connected a fiexible tubing or hose 9 in. turn connected to an outlet pipe 10 ysecured to and passing through lan end wall of the container 1. -The support 5 is suspended at the lower end of bails 11 secured to theends `of the support by nuts 12 as shown in Fig. 1- of the drawings. The center portion 13 of the bail is connected by a link 14 to a hoistf ing means or block and tackle 15 supported by a hook 16 to' an eye bolt 17 fastened to the .ceiling 18 of a room. The block and tackle may .be operated in an obvious manner for raisingand lowering the support 5 from and into the container 1. When lowered into the container l the support 5 and theformers 7 thereon, are immersed in the fluidal mass 2. Upon producing a suction by the suction means so that it will-be transmitted to the hose 9 and ports 6a into the space interiorly of the formers, the -vacuum thus created therein will cause the liuidal mass to press' against the exterior of the formers, permitting the liquid or water to'pass through the perforations of the former and interirly thereof and b'e drawn from the interior thereof into the The amount of fiber deposited upon the formers and the thicknessv of the fiberaccretion may be regulated by the time or duration of the suction action and the amount of vacuum produced within the formers. In order to aid the fibers to suitably interlace on the former, the container 1 is preferably given a vibratory movement as well as the mass therein together with the formers and supports. Due to the suction the fibers will take up a definite relation' with each otheron the former' so that the fibers will be de osited in interlacedac2 cretions whereby to orm a horn wall .of 'substantially uniform liber arrangement and of relatively soft texture which lends itself admirably to the modulation and amplification of the sound waves.- It will beapparent that the thickness ofthe horn wall may bel directly controlled by the degree of suction and its duration. And it is further manifest that' since the initial stages of the suction are stronger, due to the fact that the pores of the former are lessfree from clogging the density of the wall will begreater.

The type of former illustrated is prefer-k ably made of two portions, one of bell shape ,or formin a bell portion ofthe former and relatively smaller mesh or openings than the to a common conduit 8.to an. end of which"l inner member. Upon the exterior of the member 24 'is preferably provided a covering ordsheathing 25 of fine mesh, such asa strip of linen or like 'textile fabric. These formersare made intwo portions for the purpose of facilitating the removal of the same from the interior of the blank when the blank surrounds the same. These parts are made detachable by providing the bell portion with an .ear 26 suitably threaded or erforated to receive a rod 27 which extends ongitudinally through the tone arm and through an end wall 28 thereof andv threaded to receive thumb nuts 29 and 30. By placing the two portions `of the former together and with the rod'27 extending through the ear 26 and the end member 28 the thumb nuts may then be threaded in place and tightened so as to securely hold the tone arm to the bell portion rigidly.

A plurality of these formers may be placed upon the su port 5, as shown, with the tone arms exten ing laterally as shown in Fig. l of the drawings. The formers shown in this figure are in transverse section through the v b ll t' pipe 8, hose 9 and pipe 10 to be-drained away. e Por lon of the formers The gradual accretions ofjthe fibers on the porous former produces the roughly shaped horn 31 as shown in Fi 5'of the drawings. The formers are now raised out of the liquid and the suction continued until thefibers are consolidated, and slightly dried. At this stage the horns may either be smoothed `as by hand rolling, to sliape them. more sym metrically and eliminate the rugosites, orl

smoothing pressure by means of. pneumatic rubber bags in the form of a two-part hornshaped mould. I`n this case the' horn is placed within the mould sections and the air pres'-l sure turned on to infiate the rubber bag sections of the mold to press the mold walls against the horn. Pre erably 'this operation izo is assisted by suction. The suction being turned on after the bag mold is placed in position, which increases the sucking head and permits less bag pressure since the pores of the fiber horn are substantially closed by the'rubber bag. If desired, the horn may be given any suitable design by forming the bag walls with such a design.

The horn is now ready for drying. Heretofore, it has been customary to place the blank, still on the former, in an oven or other heating apparatus. This necessitated a large number of formers. In lieu thereof the fiber horn is removed from the porous former and placed on a single drying form during the drying operaiton. This is cheaper because it requires fewenformers to be usii' I d f eans is provide or quickl strip in the fiber horn from the porous forymer.` ucli means is shown in Fig. 4 of the drawings. i

It comprises a table 32 having supporting legs 33 and brackets 34. In the brackets 34 are slidably mounted shanks 35 of hooks 36 extending above the table 32. The lower ends of the Shanks 35 are connected by a cross rod 37 passing through a. pedal 38 pivotally supported in floor brackets 39. Coiled springs 4() may be interposed between the brackets 34 and collars 41 secured to the Shanks 35. By operating the pedal 38 the hooks 36 may be moved upwardly over the table 32 and upon releasing the pedal the springs 40 will operate to lower the hooks. In the center of the table 32 is provided a port 42 to which is connected a pipe 43 leadlng to a pressure Atank 44 or other suitable source of air pressure, the pipe 43 being provided with a control valve 45 having an operating lever 46 connected by a link 47 pivotally connected to a foot pedal 48 ivotally supported in fioor brackets 49. yoperating the pedal 48 the valve 45 may be opened or closed to through pipe 43 and port 42. In the operation of this device a former with a blank is placed upon the table 32 and the hooks 36 made to engage with the marginal portions of the former, such as the edge 50 of the bell portion thereof. Releasing the pedals 38 will permit the spring 40 to hold the hooks in place and hence the former upon the table. The springs 40 are sufiiciently strong to hold this in place for this operation. Inasmuch as the fibers are more or less intimately in engagement with the mesh of the outer members of the former, it is ordinarily difcult to remove the blank from the former. In this invention this is easily effected by opening the valve 45 and permitting air pressure to be admitted into the interior of the former and blank. This pressure immediately slightly extends the horns, thus releasing the internal fibers of the blank from the wire mesh of the former. Inasmuch as the coverermit the pressure of air to passing 21 isof finer mesh the tone arm portion will be easily removed by reason of there being less intimateV engagement between the internal fibers of the horn and this part of the former. After the horn had thus been loosened or released, the foot pedal 38 may be operated to release the hooks 36 from the former and the thumb nuts 29 and 30 removed form the rod 27 so that the bell portion 19 of the former may be removed from the interior of the larger end of the horn.

With this bell portion removed the tone arm portion may then be withdrawn toward and given a sanding operation. In addition theA stem of the horn is fitted for the ferrule.

The horn is now ready for the surface hardening treatment. This consists of a chemical treatment of the superficial fibers of the horn wall to harden them and give them tensile strength. Preferably this is accomplished by immersing the horn in the. desired substance. In the present instance the horn is dipped in a vat of glue for a desired length of time suitable to impregnate these fibers, the impregnation extending substantially one-sixteenth to one-thirty-second of an inch. This treatment now only hardens these fibers but also compacts themgand lays the fibers better. In lieu of liquid glue, rosin,

asphalt, drying oils or equivalent substances r may be used. After gluing, the horn is dried and is then again sanded to smooth condition, the ferrule is positioned and the horn is then given a surface finishing treatment, as, for instance, by stippling, and painting or by shellack varnishing or the like to give the horn walls a hard smooth finish best suited for reflecting the sound waves and for preventing the absorption of the sound.

Rather recent acoustical researches and investigations haveshown thatl the modification, distortion or other alteration of the true sound Waves emitted by the diaphragm are the result of causes other than the resonance of the sound horn itself. It has been found that irrespective of the resonance of the horn or diaphragm there is another tone produced by any particular horn which tone varies with each material and is due directly to the material itself. In order to properly identify this characteristic tone modifying property of the horn Wall I have termed is persistency. -Investigational measurements tral relatively softer fibers.

of this characteristic have shown that this effect is directly proportional to the density of the material used in the horn and is independent of shape or sizeof the amplifying horn. It is also dependent upon the thickness of the horn walls; by varying the thickness of this wall or different portions thereof, it is possible to increase or decrease the effect at will. Furthermore, by varying the density of different portions of the horn wall, various eHects of modifications of persistency can be secured, such for instance as varying the ratio of the relatively soft center to the harder exterior wood. These investigations have proven that persistency or variation of the true sound waves emitted by the diaphragm by the horn itself, is much less in a horn composed of interlaced fiber and especially one wherein the outer fibers are compressed or compacted, than in the case of metallic horns,l wooden horns or compressed fibers. Theseresults have been confirmed by actual use of a horn constructed in accordance with this invention which makes it quite obformed mold or former, whereby a horn wall of any desired thickness may be obtained and wherein a horn wall of any desired degree of density may be secured or wherein a horn wall of varying degrees of density in different portions thereof may be obtained; and it must also be apparent that by reason of this process a horn of any desired shape or configuration may be quickly and cheaply made. Also, by reason of the construction of the inner horn walls being of relatively soft texture ahorn is produced which considerably modulates the tonal qualities of the sound and tends to eliminate sustained resonance. The adaptability of the foregoing process is also due to the impregnation of the superficial fibers of the horn walls with the hardening and compacting substance, such as glue, whereby exterior layers or strata of harder, denser fibers are provided enclosing the cen- This combined relatively soft and relatively hard wall construction still more reduces sustained resonance, since any variations which tend to be -set up in the wall areg'substantially at once damped out by these alternate layers. This aids, much, in maintaining an even range of amplification. In addition, in those horns which are given the smooth, hard polished finish on the exterior surfaces of the walls, the refiection of the sound waves is considerably augmented. This also assists amplification and also increases the durability and strength of the horn.

In some instances instead of compacting the outer fibers of the horn wall by impregnation with liquid glue or the like, a somewhat similar tonal quality can be secured by forming the walls of an inner layer of pulp fiber and outer layers of ground leather. The latter is hard and provides a hard compact surface wall for the horn. The pulpl fiber and ground leather are preferably formed by suction. The leather is first sucked on, then the pulp and then the leather, to provide an even softer zone enclosed by harder zones.

` While I have herein described and upon the drawings shown one way of carrying out the invention, it is to be understood that the invention is not limited to the particular method described, but that the invention comprehends other ways and methods of practicing the same without departing from the spirit thereof.

Having thus described my invention,

I claim:

1. The method of forming sound amplifier horns which comprises immersing a porous horn-shaped former in a fibrous pulp bath, sucking the liquid of the bath through the former, removing the fiber horn from the bath enclosing the formed fiber horn in an inflatable rubber, horn-shaped mould, exerting pressure on said mold to press and smooth the walls of said fiber horn while exerting suction through the former, drying the fiber form, impregnating the superficial fibers with glue-like material, and finishing the horn.

2. In apparatus for making sound amplifiers, a former having a porous bell portion,

and a porous tone arm portion of finer mesh than the bell portion, and means for detachably securing the portion together.

3. In apparatus for making sound amplifiers, a former comprising a bell portion having an inner 'perforated member and an outer reticulated member, and a tone arm portion having an inner perforated member, an intermediate reticulated member and an outer fine mesh fabric covering.

In witness whereof, I'I hereunto subscribe my name to this specification.

JESSE BARNUM HAWLEY. 

